The synthesis of rat alveolar basement membranes will be compared under three different conditions: (a) during neonatal maturation of alveolar septa, (b) when freshly isolated pneumocytes II make these components in culture, and (c) during repair of short term inhalation damage of the alveolar lining. In preliminary experiments we found that slices of neonatal rat lung incorporated radioactive amino acids into basement membrane procollagen IV, which we extracted and identified. Similarly, we shall study the formation of other extracellular matrix components and their interactions with each other and with cells. A hypothesis is proposed to relate interactions of cell surfaces with adjacent extracellular matrix during cell migration and in the elaboration of basement membranes. To investigate this, pneumocytes II will be isolated and cultured under several conditions. The effects of precoating dishes with basement membrane components will be tested, and the relationship of cell division to extracellular matrix synthesis will be explored. The potential relative roles of synthesis and degradation of basement membrane during repair of the alveolar lining will be evaluated. The total study will provide insight into the biosynthetic relationships between alveolar cells and the basement membranes which they make and adhere to.